She has mourned every one of her corgis over the years, but she has been more upset about Willow’s death than any of them,’ a palace source told The Daily Mail.
‘It is probably because Willow was the last link to her parents and a pastime that goes back to her own childhood. It really does feel like the end of an era.’
The pet reportedly has a cancer-related illness and the monarch did not want him to suffer.
‘She does not like seeing her dogs suffer and she knows that sometimes putting a dog down is the kindest course of action – although that doesn’t make her loss any less,’ added the source.
Willow lived to 15 years of age and was seen in the Queen’s official portrait for her 90thbirthday and appeared alongside Daniel Craig in the James Bond Olympics sketch.
It is believed that Willow is buried in the Windsor castle grounds.
The Queen still has two dorgis, a cross between a corgi and a dachshund, named Vulcan and Candy.